function fn {
    echo -n "$1  "
    if [ $1 -eq 6 -o $1 == 7 ]; then
        echo '周末'
    elif [ $1 == 5 ]; then
        echo '快乐周五'
    elif [ $1 == 1 ]; then
        echo '周一啦'
    else
        echo 'normal day'
    fi

}
fn 1
res=$(fn 6)
echo ====== $res
# fn 2
# fn 3
# fn 4
# fn 5
# fn 6
# fn 7